(1) Field of the Invention
This invention relates to nondestructive testing for defects in metals and more particularly, for defects in boiler tubes or water walls used in the electric utility industry. More particularly, this invention is used for detection of erosion which occurs as a result of abrasive particles contained in coal feedstock. The erosion may be both internal and external. This invention provides a nondestructive inductance-based test technique that reliably assesses tube or wall thinning conditions and, thus, enables the prediction of future failure events.
(2) Description of Related Art
In the prior art, nondestructive techniques for measuring boiler tube erosion or water wall erosion comprise eddy-current testing, dye-penetrant testing, ultrasound testing, and x-ray testing. These systems are not cost effective because they are extremely slow, require use of delicate instruments which are incapable of survival in an industrial setting, require instruments which are very expensive, and use instruments which require highly skilled operators. It has been found that when using such prior art techniques, they are not cost effective for performing near 100% effective tests for some defects in large industrial systems even though such defects usually cause very costly failures when they occur.